JP5550489B2 - Non-reflective termination resistor circuit - Google Patents

Description

  The present invention relates to a non-reflection termination resistor circuit, and more particularly to a non-reflection termination resistor circuit in a dielectric waveguide used in a high frequency band.

  In constructing various circuits using a waveguide filled with a hollow or dielectric material, a non-reflective termination (dummy termination) is required to suppress unnecessary reflected waves. A three-dimensional wave absorber having a tapered shape such as a pyramid or a cone was inserted into the wave tube.

  FIG. 6 shows a diagram of the non-reflective termination described in Non-Patent Document 1. In the figure, reference numeral 100 denotes a hollow waveguide, and 101 denotes a radio wave absorber having a tapered shape inserted therein. One end of the hollow waveguide 100 is an electrically short-circuited end 102 that is electrically short-circuited, and the remaining end is an input terminal 103 for a high-frequency signal. In the circuit, the high frequency signal input to the hollow waveguide 100 is absorbed by the radio wave absorber 101. At this time, in order to keep the reflection coefficient viewed from the input terminal 103 sufficiently small, the amount of insertion of the radio wave absorber 101 increases as it proceeds from the input terminal 103 to the electrical short-circuit end 102. As the shape of the absorber 101, a tapered shape is generally adopted.

  On the other hand, as a dielectric waveguide essentially the same as the hollow waveguide 100 described above, the upper and lower surfaces of the dielectric substrate are metallized with a conductor, and the side surfaces thereof are similarly metallized or via holes that are electrically equivalent thereto. There is a so-called “post wall waveguide” or SIW (Substrate Integrated Waveguide), which is configured by providing rows. FIG. 7 is a structural diagram of the post wall waveguide disclosed in Patent Document 1. In the figure, 110 is a dielectric substrate, 111a and 111b are conductors metallizing the upper and lower surfaces of the dielectric substrate 110, and 112 is a metallized via hole. The via holes 112 are a plurality of conductive holes (through holes) arranged in two rows provided in the dielectric substrate 110, and are arranged so that each row is parallel to the side surface of the dielectric substrate 110. . The post wall waveguide of FIG. 7 is electrically equivalent to a rectangular waveguide filled with a dielectric, but unlike a conventional waveguide, it has relatively high accuracy and mass production using a substrate processing process. Since processing with excellent properties is possible, application to antennas and various high-frequency circuits has been attempted.

  As a conventional non-reflective termination made of this type of post-wall waveguide as shown in FIG. FIG. 8 shows a configuration diagram thereof. In the figure, 120 is a dielectric substrate, 121a and 121b are conductors metallizing the upper and lower surfaces of the dielectric substrate 120, 122 is a metallized via hole, and these constitute a post wall waveguide. In the figure, one end of the waveguide is electrically short-circuited by a via-hole array, and a via hole in which a resistor is loaded in the form of a tapered shape from the short-circuited end toward the input terminal. 123 is arranged. The configuration substantially follows the configuration of the non-reflective termination in the hollow waveguide shown in FIG. 6, and the tapered wave absorber in FIG. 6 is arranged in a tapered shape in FIG. By doing so, a non-reflective terminal is formed.

JP-A-6-53711 Japanese Patent Laid-Open No. 11-8502

R.E.Collin, "Foundations for Microwave Engineering", Second Edition, McGRAW-HILL INTERNATIONAL EDITIONS, Electrical Engineering Series, 1992, p. 395

  When the post wall waveguide non-reflective terminal shown in FIG. 8 is to be realized, it is necessary to form a thin film resistor on the inner surface of the via hole 123 in the substrate processing process described above. However, while a thin film resistor can be formed relatively easily on the surface of the substrate, forming it inside the substrate is accompanied by great difficulty in processing together with controlling the film thickness, that is, the resistance value. Furthermore, when an error occurs in the resistance value, there is a problem that the reflection coefficient of the non-reflection terminal increases.

  Therefore, instead of the via hole 123 in FIG. 8 described above, the tapered wave absorber 101 shown in FIG. 6 may be embedded in the post wall waveguide shown in FIG. There is a problem that it is very difficult to fill the body 101 into the dielectric substrate 120 in terms of the processing process.

  In addition, the process of embedding such a radio wave absorber is more complicated than the process of processing a planar circuit board such as a conventional microstrip line or coplanar line, and is not advantageous in terms of manufacturing cost. There is also the problem of incurring profits.

  The present invention has been made to solve such a problem, and realizes a non-reflective termination by a simple structure in which a thin film resistor is simply loaded on the upper surface of a dielectric substrate constituting a post wall waveguide. An object of the present invention is to obtain a non-reflective termination resistor circuit that facilitates the process, stabilizes the reflection coefficient of the non-reflective termination, and can reduce the manufacturing cost.

The present invention relates to a dielectric waveguide configured by metallizing the upper and lower surfaces of a dielectric substrate with a conductor and metallizing the side surfaces in the same manner or providing a via hole array that is electrically equivalent thereto, and the dielectric Provided on the substrate and provided at the other end of the dielectric substrate opposite to the input end where the signal is input and electrically short-circuited to reflect the signal input from the input end A short-circuit end, a part of the upper surface of the dielectric substrate is a thin film resistor instead of the conductor, and an inductive post having an electrically inductive characteristic is provided between the input end and the thin film resistor. This is a non-reflective terminal resistor circuit.

The present invention relates to a dielectric waveguide configured by metallizing the upper and lower surfaces of a dielectric substrate with a conductor and metallizing the side surfaces in the same manner or providing a via hole array that is electrically equivalent thereto, and the dielectric Provided on the substrate and provided at the other end of the dielectric substrate opposite to the input end where the signal is input and electrically short-circuited to reflect the signal input from the input end A short-circuit end, a part of the upper surface of the dielectric substrate is a thin film resistor instead of the conductor, and an inductive post having an electrically inductive characteristic is provided between the input end and the thin film resistor. The non-reflective termination resistor circuit is characterized by the fact that the non-reflective termination is realized by a simple structure in which a thin film resistor is loaded on the upper surface of the dielectric substrate constituting the post-wall waveguide. Easily to, it ensures stable reflection coefficient of reflection-free termination, it is possible to suppress the manufacturing cost.

It is a figure which shows the non-reflection termination | terminus resistor circuit by Embodiment 1 of this invention. It is a figure which shows the equivalent circuit of the non-reflective termination resistance circuit by Embodiment 1 of this invention. It is a figure which shows the example of a specific structure of the non-reflective termination resistor circuit by Embodiment 1 of this invention, and its reflection characteristic analysis result. It is a figure which shows the non-reflective termination resistor circuit by Embodiment 2 of this invention. It is a figure which shows the conventional non-reflective termination which consists of a microstrip line. It is a figure which shows the conventional non-reflective termination | terminus which consists of hollow waveguides. It is a figure which shows the structure of the conventional post wall waveguide. It is a figure which shows the conventional non-reflective termination which consists of a post wall waveguide.

Embodiment 1 FIG.
FIG. 1 is a diagram showing a non-reflection termination resistor circuit according to Embodiment 1 of the present invention. In FIG. 1, 1 is a substantially rectangular (rectangular) dielectric substrate, 2 a and 2 b are conductors that metalize the upper and lower surfaces of the dielectric substrate 1, and 3 is metallized provided on the dielectric substrate 1. A via hole. The via holes 3 are arranged in a substantially U-shape along the three sides (outer edges) of the dielectric substrate 1 so as to be parallel to the three sides. Each via hole 3 is formed by drilling the dielectric substrate 1 and then applying a high-resistance paste to the surface of the hole. The conductors 2a and 2b are formed by applying a high-resistance paste to the upper and lower surfaces of the dielectric substrate 1. However, these forming methods are merely examples, and the present invention is not limited thereto. In the present embodiment, one end of the dielectric substrate 1 is electrically short-circuited by a via-hole array formed of via-holes 3 to form a short-circuited end 8. Thereby, in the present embodiment, the dielectric substrate 1, the conductors 2a and 2b, and the via hole 3 constitute a post wall waveguide (dielectric waveguide).

  In FIG. 1, 4 is a thin film resistor formed on the upper surface of the dielectric substrate 1, and 5 is formed inside the post wall waveguide and exhibits electrically inductive characteristics. , 6 is an input terminal to which a high-frequency signal is input. The via hole 5 may be formed by, for example, applying a low resistance paste having inductivity to the surface of the hole after the dielectric substrate 1 is subjected to hole processing, but is not limited thereto. Of course, other formation methods may be used. The thin film resistor 4 may be formed on the dielectric substrate 1 by sputtering or the like, for example. In the present embodiment, since the thin film resistor 4 is formed on the surface of the dielectric substrate 1 in this way, it can be easily formed, and the film thickness, that is, the resistance value can be controlled easily and accurately. Can be performed, and an error in the resistance value can be prevented from occurring. The non-reflection termination resistor circuit according to the present embodiment is thus composed of the dielectric substrate 1, the conductors 2a and 2b, the via hole 3, the thin film resistor 4, the via hole 5, the input terminal 6, and the short circuit end 8. Yes. The via hole 5 is provided in a region (or boundary) between the dielectric waveguide portion constituted by the input terminal 6 and the thin film resistor 4. In FIG. 1, a total of four via holes 5 are provided in the vicinity of the input terminal 6. The via holes 5 are provided in two rows, and each of the rows is not parallel to the side (outer edge) of the dielectric substrate 1, and the mutual distance (taper) from the thin film conductor 4 toward the input terminal 6. It is arranged in a substantially square shape so as to be a tapered shape with a wide (width). In the portion where the thin film resistor 4 is provided, the conductor 12 is not provided, and the thin film resistor 4 is provided directly on the upper surface of the dielectric substrate 1.

  Next, the operation of the non-reflection termination resistor circuit according to this embodiment of the present invention will be described. In the present embodiment, one end of a lossless post wall waveguide is electrically short-circuited by a via hole array of via holes 3 and a loss is added mainly in the series direction of the post wall waveguide by a thin film resistor 4. In addition, an inductive post comprising a via hole 5 is loaded adjacent to the input terminal 6. Here, when a high frequency signal is incident on the input terminal 6, the signal is gradually attenuated by the thin film resistor 4 and reaches the short circuit end 8, and the signal reflected by the short circuit terminal 8 returns to the thin film resistor 4 again, and the thin film resistor 4 is further attenuated in the same manner, and almost no reflected wave reaches the input terminal 6. In general, it is known that a lossy transmission line operates as an almost non-reflective termination if a sufficient length is ensured. Therefore, according to the present embodiment, as shown in FIG. Even if a resistor is not provided, a non-reflection termination circuit can be easily realized by providing a thin film resistor that can be easily formed on the surface of the substrate.

  However, as described above, the reflected wave viewed from the input terminal 6 may not always be sufficiently suppressed by simply providing the thin film resistor 4 on the upper surface of the post wall waveguide. In order to suppress the wave, a via hole 5 that functions as an inductive post is further provided in the vicinity of the input terminal 6. However, the via hole 5 is not necessarily provided, and may be provided as necessary. Hereinafter, description will be made based on an equivalent circuit of a non-reflection termination according to the present embodiment shown in FIG.

  In this embodiment, in a lossy distributed constant transmission line to which a certain amount of series resistance is added per unit length, one end thereof is electrically short-circuited, and an inductor is shunted at the other input end. It can be regarded as a loaded circuit. In the figure, an input impedance Zwg of a circuit that allows for a lossy transmission line is given by the following equation (1).

    Zwg = Ztanh (γd) (1)

  Here, Z and γ are the characteristic impedance and propagation constant of the lossy transmission line, and are complex quantities given by the following equations (2) and (3), respectively. D is the length of the transmission line loaded with the resistor. Further, tanh is a hyperbolic tangent of a hyperbolic function (tanh (x) = (exp (x) −exp (−x)) / (exp (x) + exp (−x))).

Z = [(R + jωL) / (jωC)] ^1/2 ≡Zr + jZi (2)

    γ = [jωC (R + jωL)] 1/2 ≡α + jβ (3)

  Here, α is the attenuation constant of the transmission line, and as the series resistance R corresponding to the thin film resistor 4 increases, α also increases. Here, assuming that the resistance value of the thin film resistor 4 is relatively large and that γd in the expression (1) is sufficiently large, the expression (1) becomes the following expression (4) from the expression (2). The input impedance of the circuit that anticipates is substantially equal to the characteristic impedance Z of the line.

    Zwg = Ztanh (γd) ≈Z = Zr + jZi (4)

  On the other hand, by squaring both sides of the formula (2) and paying attention to the imaginary part, a relational expression represented by the following formula (5) is obtained.

    -Zi = R / (2ωCZr) (5)

  Further, since the right side of the equation (5) is clearly positive due to the nature of the passive circuit, it is derived that the following equation (6) is obtained.

    Zi <0 (6)

  Therefore, from the equations (4) and (6), the impedance Zwg in anticipation of the lossy transmission line in FIG. 2 becomes a capacitive impedance in which the imaginary part Zi is negative, so that reactive energy is accumulated in the circuit. Therefore, the characteristic as a non-reflective terminal cannot be obtained, and residual reflection exists. Therefore, the via hole 5 in the present embodiment functions as an inductive post in the post-wall waveguide, and has a function of reducing residual reflection as much as possible by canceling the above-described capacitive impedance and improving the characteristics as a non-reflection termination. Plays. FIG. 3A shows an example of the structure of the non-reflection termination resistor circuit according to the present embodiment, and FIG. 3B shows an electromagnetic field analysis result by the finite element method having the same structure. The configuration of FIG. 3A is naturally the same as that of FIG. 1, but in FIG. 3A, the number of via holes 5 is large, and the portion where the via holes 5 are tapered is a thin film. The only difference is that it is provided along the side (outer edge) of the dielectric substrate 1 except for the vicinity of the resistor 4. However, such a change in the number and arrangement of the via holes 5 may be made as appropriate, and is not limited to FIG. 1 or FIG. An important feature of the circuit configuration of the present embodiment is that one end of the dielectric waveguide is short-circuited by a via hole array of via holes 3, and a part of the conductor 2a on the dielectric substrate constituting the dielectric waveguide is made a conductor. It is about the structure made into thin film resistor 4 without. From FIG. 3B, it can be seen that the circuit configuration based on the present embodiment can provide a sufficiently small non-reflective termination with a reflection coefficient of −20 dB or less over a practically sufficient specific bandwidth.

  As described above, according to the present embodiment, in the post wall waveguide whose tip is short-circuited as the short-circuited end 8, the thin film resistor 4 is provided on the upper surface of the dielectric substrate 1 constituting the waveguide, and its input By providing the terminal 6 with the via hole 5 functioning as an inductive post, a non-reflection termination circuit having a small reflection coefficient can be obtained. According to this configuration, compared to a conventional non-reflective termination configured by mounting a via hole loaded with a radio wave absorber or a resistor inside a substrate, manufacturing is easy and manufacturing cost can be reduced. It is possible to realize a non-reflective terminal for a post-wall waveguide that can stabilize the reflection coefficient of the non-reflective terminal.

  In the description of the first embodiment, a plurality of via holes 3 are formed along a pair of opposing side surfaces 9 other than the side surface of the dielectric substrate 1 where the input terminal 6 and the short-circuit end 8 are provided. However, the present invention is not limited to this, and the set of side surfaces 9 is metallized with conductors similar to the conductors 2a and 2b that metallize the upper and lower surfaces of the dielectric substrate 1. You may do it. In this case, the conductor is metalized so that the conductor for metallizing the side surface 9 is electrically equivalent to the via hole row.

  Further, in the description of the first embodiment, the example in which the shape of the thin film resistor 4 provided on the dielectric substrate 1 is substantially rectangular (rectangular) has been described. The shape may be tapered, and the taper width may be increased from the input terminal 6 toward the short-circuit end 8. In this case, the reflection coefficient can be further reduced.

  In the description of the first embodiment, an inductive post exhibiting an electrically inductive characteristic is provided in a region (boundary) between the input terminal 6 that is a dielectric waveguide portion and the thin film resistor 4. However, the present invention is not limited thereto, and a high-impedance transmission line having a smaller tube width than that of the input terminal 6 may be provided over a certain length.

Embodiment 2. FIG.
FIG. 4 is a top view showing a non-reflection termination resistor circuit according to Embodiment 2 of the present invention. In FIG. 4, 11 is a substantially rectangular dielectric substrate, the upper surface of which is partially metallized by a conductor 12, and the lower surface thereof is metallized by a conductor (not shown) over the entire surface. The difference from the first embodiment is that no conductor is provided on the entire top surface of the dielectric substrate 11. Reference numeral 13 denotes a via hole, which is arranged in a substantially U-shape along the three sides (outer edges) of the dielectric substrate 1 so as to be parallel to the three sides, and the post-wall waveguide. A via hole row corresponding to the side wall is formed. In FIG. 4, one end of the dielectric substrate 11 is electrically short-circuited by a via-hole array formed of via-holes 13 to form a short-circuited end 18. In the present embodiment, the dielectric substrate 11, the conductor 12 on the upper surface of the dielectric substrate 1, the conductor on the lower surface of the dielectric substrate 11, and the via hole 13 constitute a post wall waveguide.

  In FIG. 4, 14 is a thin film resistor formed on the upper surface of the dielectric substrate 11, 15 is a via hole formed in the post wall waveguide and operating as an inductive post, and 16 is a microstrip into which a high frequency signal is input. An input terminal consisting of a track. In FIG. 4, the conductor 12 is provided on the dielectric substrate 11 so as to have a substantially rectangular shape, and the position of the conductor 12 is provided near the short-circuit end 18. That is, the conductor 12 is not provided in the portion where the input terminal 16 and the microstrip line-post wall waveguide converter 17 described later are provided. The thin film resistor 14 is provided at a position surrounded by the conductor 12, and the position is close to the short-circuit end 18, and is provided in the vicinity of a microstrip line-post wall waveguide converter 17 described later. Not. In the portion where the thin film resistor 4 is provided, the conductor 12 is not provided, and the thin film resistor 4 is provided directly on the dielectric substrate 11. In FIG. 4, reference numeral 17 denotes a signal input from the input terminal 16 that is transmitted to the post-wall waveguide, and a reflected signal from the post-wall waveguide obtained by reflecting the signal at the short-circuit end 8 is input. It is a microstrip line-post wall waveguide converter for transmitting to the terminal 16. The microstrip line-post wall waveguide converter 17 is configured by a microstrip line having a predetermined value between the microstrip line width w1 of the input terminal 16 and the line width w2 of the post wall waveguide as the line width w3. (W1 <w3 <w2). The microstrip line-post wall waveguide converter 17 is connected between the input terminal 16 and the post wall waveguide, and when the input terminal 16 and the post wall waveguide are composed of different types of transmission lines, Conversion means for converting signals to different transmission lines and transmitting signals between them.

  As shown in FIG. 4, the via hole 15 is provided in a portion where the conductor 12 is provided and in a portion between the thin film resistor 14 and the microstrip line-post wall waveguide converter 17. The via holes 15 are provided so as to constitute two rows of via holes. In the vicinity of the thin film resistor 14, these two rows are provided in a tapered shape, and the taper width increases toward the input terminal 16. However, the other via hole 5 is provided along the outer edge of the conductor 12 (or the side (outer edge) of the dielectric substrate 11). For example, the via holes 13 and 15 are manufactured in the same manner as the method for forming the via holes 3 and 5 described in the first embodiment. Further, the thin film resistor 14 is formed by, for example, a sputtering method as in the first embodiment. The microstrip line constituting the input terminal 16 and the microstrip line-post wall waveguide converter 17 is, for example, a technique of applying a metal paste (conductive paste) in a predetermined pattern shape, a so-called screen printing technique. It may be formed by use, or may be formed by vapor deposition using a resist or the like. In addition, these manufacturing methods are not limited to this, Of course, you may form using another formation method.

  Next, the operation of the non-reflection termination resistor circuit according to Embodiment 2 of the present invention will be described. This circuit connects the input terminal 16 to the microstrip line by connecting the microstrip line-postwall waveguide converter 17 to the non-reflective termination resistor circuit comprising the post wall waveguide of the first embodiment described above. The only difference is that it has the same structure as that of the first embodiment.

  On the other hand, as a conventional non-reflective termination made of a normal microstrip line, a circuit having a relatively small thin film resistor and a grounding via hole as shown in FIG. 5 is used (for example, Japanese Patent Laid-Open No. 2006-352563). reference).

  In FIG. 5, reference numeral 130 denotes a dielectric substrate, and the back surface is entirely metallized with a conductor. Reference numeral 131 denotes a thin film resistor, 132 denotes a ground via hole, and 133 denotes a line conductor constituting a microstrip line. Further, the line width w of the microstrip line shown in the figure is substantially the same as the line width of the microstrip line shown in FIG. 4, and is considerably smaller than the line width of the post wall waveguide. In this circuit, each thin film resistor has a value of about 2Zo (Zo is a signal source impedance), and a non-reflective terminal resistance circuit having an impedance Zo is formed by combining two in parallel. .

  Here, consider the power resistance of the two non-reflective terminations described above. First, regarding the conventional non-reflective termination of the microstrip line in FIG. 5, the electromagnetic energy is concentrated in a relatively narrow cross section of the microstrip line, so that the power density per unit cross sectional area becomes large and the thin film resistor 131 is used. As a result, the withstand power of the non-reflection terminal is relatively small. Although it is possible to improve the power resistance of the thin film resistor itself while maintaining the resistance value by keeping the aspect ratio of the thin film resistance dimension of FIG. 5 constant, it is possible to improve the power resistance of the thin film resistor itself at high frequencies. It is extremely difficult to keep the reflection coefficient small due to an increase in capacitance and parasitic reactance caused by an increase in structural discontinuity with the microstrip line connected to the resistor. Therefore, it is extremely difficult to realize a non-reflection termination with high power durability by combining a microstrip line and a thin film resistor.

  On the other hand, according to the present embodiment shown in FIG. 4, a signal input to the input terminal 16 composed of a microstrip line is first converted into a post wall waveguide by the microstrip line-post wall waveguide converter 17. Is done. Here, the cross-sectional dimension of the post-wall waveguide is much larger than that of the microstrip line constituting the input terminal 16, and the power density per unit cross-sectional area is smaller than that of the microstrip line. Furthermore, in the configuration of FIG. 4, the thin-film resistance of the non-reflective termination constituted by the post-wall waveguide is naturally considerably larger than that of FIG. Can do.

  As described above, in the present embodiment, the same effects as those of the first embodiment described above can be obtained, and further, the microstrip line--with respect to the non-reflection termination resistor circuit composed of the post wall waveguide and the thin film resistor. By connecting the post-wall waveguide converter 17 and using it as a microstrip line non-reflective termination, it is more resistant to the conventional microstrip line non-reflective termination consisting of a relatively small thin film resistor and a ground via hole. It is possible to obtain a non-reflective terminal with high power.

  In the above description of the second embodiment, an example in which a microstrip line is provided as the microstrip line-post wall waveguide converter 17 has been described. The waveguide converter 17 may be composed of a coplanar line, a coaxial line, a hollow waveguide, or the like.

  1, 11, 110, 120, 130 Dielectric substrate, 2a, 2b, 12, 111a, 111b, 121a, 121b, 133 Conductor, 3, 5, 13, 15, 112, 122, 132 Via hole, 4, 14, 131 Thin film resistor, 6, 16, 103 Input terminal, 8, 18 Short-circuited end, 9 Side, 123 Resistive via hole, 17 Microstrip line-post wall waveguide converter, 100 Hollow waveguide, 101 Wave absorber, 102 Electricity Short circuit end.

Claims (4)

A dielectric waveguide configured by metallizing the upper and lower surfaces of the dielectric substrate with a conductor and metallizing the side surfaces in the same manner or providing a via hole array that is electrically equivalent thereto;
An input terminal provided on the dielectric substrate and receiving a signal;
A short-circuit end provided on the other end of the dielectric substrate facing the input end, electrically short-circuited, and reflecting the signal input from the input end;
A portion of the top surface of the dielectric substrate is a thin film resistor instead of the conductor ,
An anti-reflection termination resistor circuit , wherein an inductive post having electrically inductive characteristics is provided between the input terminal and the thin film resistor . The non-reflection termination resistor circuit according to claim 1 , wherein the thin film resistor has a rectangular shape. 2. The non-reflection termination resistor circuit according to claim 1 , wherein the thin film resistor has a tapered shape, and the taper width increases toward the short-circuit end. When the input end and the dielectric waveguide are connected between the input end and the dielectric waveguide, and the input end and the dielectric waveguide are composed of different types of transmission lines, conversion of signals to the different types of transmission lines is performed. Te, reflection-free termination resistor circuit according to any one of claims 1 to 3, further comprising a converting means for performing the transmission of signals therebetween.

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